Efeitos das tecnologias emergentes não térmicas empregadas no processamento de suco prebiótico de maçã

Abstract

The increase in apple juice consumption of the demand for functional foods has shown the need for more research regarding prebiotics juices apple. The traditional heat conservation usually imparts quality loss of fruit juices. The objective of this study was to verify the effects of new non-thermal technologies on the quality of fruit juices containing prebiotic oligosaccharides with regard to its functional property. At first, it was applied plasma and high pressure processing in apple juice with added fructo-oligosaccharides (FOS, 7 % w/v). In the case of plasma it was tested two types of exposure (direct and indirect) and different processing times (15, 30, 45 and 60 seconds). The high pressure processing was carried out at 450 MPa for 5 min. Colour, oligosaccharides concentration and organic acids were evaluated. Regarding colour, all juice samples treated by plasma and by high pressure demonstrated a significantly more vivid colour according to on the Chroma value. The results showed some depolymerisation of FOS, increasing the concentration of 1-kestose (oligosaccharides with 3 monomers). However, after the plasma treatment, the total concentration of FOS still meets the standards required by law, confirming that plasma is a suitable non-thermal technology for apple juice containing FOS. The high pressure treated samples presented similar behaviour. Regarding the organic acids concentration, malic acid was the predominant one and presented a decay after both plasma exposure modes (direct and indirect). The same happened for citric acid. For the juices treated by high pressure, there was a significant increase in the concentration of both acids when compared to the control. In the second stage of the research, the biotechnological process started. Through a fermentation using the bacterium Leuconostoc mesenteroides it was produced the dextransucrase enzyme. The enzyme was purified and used to convert the simple sugars present in the apple juice in prebiotic gluco-oligosaccharide. After synthesizing the prebiotic juice plasma treatment was applied under the same conditions of the first stage. Ozone was also applied using different loadings: 0.057; 0.128; 0.230; 0.386 and 0.671 mg O3 / mL. After the treatments the concentrations of simple sugars (fructose, glucose and sucrose), oligosaccharides and organic acids by HPLC were measured .The total phenolic content was determined by Folin-Ciocalteu method and the antioxidant activity by ABTS. For both treatments oligosaccharides depolymerisation was observed, but the total concentration of oligosaccharides attested that the juices remained with prebiotic activity. The oligosaccharides were better preserved after ozone treatment, followed by plasma with direct exposure. The citric acid concentration presented significant difference only for juices treated by ozone, while malic acid had a significant decay for both treatments. In the case of plasma there were changes in both acids concentration. The phenolic content unchanged after plasma direct exposure and also after ozone treatment, showing a decrease after indirect exposure (0.73 ± 0.10 to 0.53 ± 0.02). The antioxidant activity presented slight differences after ozone treatment. After plasma, the antioxidant activity presented significant increase for both exposures kind. Then non-thermal technologies studied herein can be applied in prebiotic juices, preserving their functionality and quality.